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Monday 9 May 2016

Let's not diet like it's 1999. How a generation of nutritionists and dietitians was taught to make weight loss more difficult than it needs to be.

Diet advice is so varied today, and nutrition science is changing so fast, that it’s easy to forget how monolithic low-fat weight loss advice was only a few years ago.

We recently discovered a US nutrition textbook from 1999. This book has a good claim to represent the orthodoxy. It contains the views of multiple experts in the various areas of nutrition.

By far the bulk of the book is sound nutrition science, and still worth learning – but there are areas where it wanders away from science fact and stakes a position that seems questionable today.

It’s the section on Energy Balance and Weight Control that’s the real eye opener.

It’s very much about calories in vs calories out. Well, of course it is, but with the 1999 diet plan, food intake and activity level need to be focused on to a high degree.

“1. The plan should meet nutritional needs, except for energy. To do that, it should follow the Food Guide Pyramid, emphasizing low-fat and nonfat choices and adequate fluids (6-8 cups per day). Overall this controlled eating should remain a satisfying and pleasurable experience.”
[Note that this book does include mention of the novel 1994 Mediterranean Pyramid, but because it can supply more fat – 25-35% shock horror – and one or two full-fat dairy foods, weight gain is considered a possible risk, so it’s kept out of the Energy Balance section!)
“2. Slow and steady weight loss, rather than rapid weight loss, should be stressed. A loss of 1 or so pounds of fat storage per week is desirable. Once about 10% of excess weight is lost, maintenance of that loss for 6 months is recommended before more weight loss is attempted”
“Total fat intake for the day is the focus. This approach makes sense, because a lifelong restriction of energy intake is almost impossible, whereas a low-fat diet is easy to follow indefinitely if it allows consumption of enough foods – especially fruits, vegetables, and whole grains – to satisfy hunger. However, this method will only work if high-calorie fat-free foods – such as fat-free cakes and cookies – are not overeaten.”
What is the Food Guide Pyramid of 1999? In terms of the weight loss diet, it is 6 servings of bread, cereals, rice or pasta (serving = 1/2 cup or 1 slice), 2-4 servings of fruit, 3-5 servings of vegetables, 2-3 servings of nonfat or low-fat milk/dairy products (serving = 1 cup), and 4-6 oz lean meat or alternatives [this category includes dried beans, which might have been more usefully deployed as cereal alternatives]
Why so much carbohydrate over the more satiating fat (in an earlier section of “hard science” it is explained that chylomicrons are satiating)?

The reason given for preferring a high-carbohydrate diet is slightly gob-smacking today; because carbohydrate stimulates energy expenditure. This is the old metabolic advantage argument sometimes used by both sides of the carb vs fat debate..

The following are listed among “practices that can stimulate metabolism while dieting”.

  • “- Fidget when sitting and standing [Seriously? This seems pretty desperate! Try telling a person who fidgets NOT to fidget, and you’ll see how practical this advice is.]
  • – Eat breakfast, so food intake is spread throughout the day. Each time food is consumed, metabolism increases
  • – Follow a carbohydrate-rich diet; much of this is further processed by the liver, which uses energy.”
So the conversion of glucose to fat by the liver is one of the advantages of a high-carb diet, while the conversion of fat to ketones on low carb diets is a problem?

We know that the low-fat diet will produce weight loss in people who are satisfied enough by it, or have enough willpower, to restrict calories.
The problem is, what happens to people who become hungrier on such a diet, and what happens when such Food Pyramid diet advice is applied to the whole population without calorie restriction, and in the presence of sweet treat foods, in the belief that this will also help with energy balance and weight control? The frequent high-carbohydrate meals stimulate high insulin levels, and the processing of carbohydrate by the liver results in increased ectopic fat and insulin resistance, tending to promote increased fat storage and appetite and higher blood sugars.

Further, some forms of calorie restriction can produce a lasting drop in the metabolic rate, which then makes it hard to avoid regaining weight. This is why the low-fat diet plan has you eating all the time, losing weight slowly (if at all), and trying to fidget; to keep up the metabolism. But low carb diets, and plain fasting, don’t depress the metabolic rate. They don’t set you up to fail as the Biggest Loser diet, which is Eat Less, Move More taken to its (il)logical extreme, does. This is explained very neatly by Jason Fung in a recent post at Diet Doctor, using the evidence from 3 recent metabolic studies by Kevin Hall.
This is the real “metabolic advantage” of LCHF – not a boost to metabolism as once thought, but its protection.

The problem with the 1999 advice is not the low—fat diet as such, but the lack of respect for and serious scientific consideration of alternative ways of eating, which is explicable here by the predominating fear of animal fat and cholesterol, and the higher calorie-per-gram value of fats. The existence of an officially-sanctioned Food Guide Pyramid must also have tied the hands of textbook writers – if they presented a convincing case for an alternative, what publisher would take a risk on their work? Perspectives In Nutrition gives several pages for experts to debate, sometimes hotly, divergent views on undecided topical issues such as the use of vitamin E supplements, but fails to provide the diversity of expert opinion about weight control that surely (?) still existed in 1999. The failure to consider the role of insulin in the energy balance response to diet, and to look into the contradictions and controversies around diet, cholesterol and health, undermines all the good science and good intentions in this book and results in the building of a massive structure of difficult-to-follow advice on a shaky foundation. A whole generation of today’s nutritionists and dietitians were given no reasons to think that carbohydrate restriction might be a safe and useful strategy, and were, it seems, trained to dismiss it out of hand as a ‘fad diet’.

The one-size-fits-all low fat, high carbohydrate diet plan, which has now been shown to be, on average, less effective than just about anything else you could try, really did preside over nutrition teaching during the obesity epidemic, however much this might be denied today.

It is a relief to turn from the Energy Balance section of Perspectives in Nutrition to the sound sense of John Yudkin, writing in 1963.

“The ability to separate palatability from nutritional value leads to the consumption of increasing amounts of food, chiefly rich in carbohydrate, in circumstances in which one would have expected a reduction in the intake of carbohydrate [i.e. in periods of increased income, when one would reasonably expect intake of fat and protein to increase]. There is evidence that this distortion of the diet plays a part in the increased incidence of obesity and dental caries, and also perhaps in the increased incidence of myocardial infarction, peptic ulcer, diabetes, and other diseases.”
“Another consequence of the increase in food consumption and the decrease in physical activity can be seen in the rise of the number of obese children and adults. The thesis that food intake is high chiefly because of the high palatability of modern carbohydrate-containing foods is supported by the fact that very effective weight reduction follows simple omission from the diet of a large part of these foods, with unrestricted eating of carbohydrate-free foods such as meat, fish, eggs, cheese, butter, and cream. We have shown that, in this sort of diet, the reduction in caloric intake is associated with a negligible increase in protein intake, but no increase -sometimes a fall- in fat intake. It is sometimes supposed that obesity is usually caused by an uncontrollable desire to eat. The fact is that those who cannot keep to their carbohydrate-restricted diet have, rather, an uncontrollable desire to eat highly palatable sugar-containing foods, to which they have, it seems, become addicted.”
This was, although not the only advice available, a very well-accepted and uncontroversial explanation of obesity and weight loss in the 1960’s, as seen in part 3 of this public information film about childhood obesity.

A Cruel Kindness 1967

People were not told to restrict fat or animal fats in the 1960’s. (The subjects in Yudkin’s studies ate about 100 grams of fat a day, both before and after restricting carbohydrate). Once animal fat in the diet was reduced by public decree, and carbohydrate intake increased, the numbers of those who were overweight increased. By 1999 the problem was recognised and great intellectual effort went into proposing solutions, but the simplest classical solution was overlooked, perhaps because the problem in 1999 seemed much more complex than it had in 1963 (or in 1825, when Brillat-Savarin first introduced the idea of the “fattening carbohydrate”), thanks in no small measure to Ancel Keys and the diet-heart hypothesis.

It became a case where “The weakness of the remedy lies in its simplicity”. The growth of the academic nutrition establishment after Ancel Keys’ huge success, and the need to keep that workforce employed, meant that arguments as simple as Yudkin’s became unwelcome, even if their basic truth could be demonstrated. In 1999, simple propositions were what defined quacks and fad diets. Yet complex instructions have a limited utility to the general public.

Surely, rather than always glamourising the complexity of science and the “multifactoral” nature of disease, it is a better approach to some public health problems to find the most true of the simple propositions, and make sure everyone knows them?


1 comment:

Anonymous said...

Graham, you state:

'A whole generation of today’s nutritionists and dietitians were given no reasons to think that carbohydrate restriction might be a safe and useful strategy, and were, it seems, trained to dismiss it out of hand as a ‘fad diet’.

The one-size-fits-all low fat, high carbohydrate diet plan, which has now been shown to be, on average, less effective than just about anything else you could try, really did preside over nutrition teaching during the obesity epidemic, however much this might be denied today.'

Unfortunately, and sadly, this is true. A whole generation were taught that nobody else had any formal or specialist training in nutrition and therefore have no right to comment on nutrition - you only have to look at official website twitter feed to see unsavoury comments about 'Dr's not having any formal nutrition training'. Everyone else was dismissed as promoting 'fad diets', as you correctly state. If it wasn't for the elitist and utterly disgraceful attitude towards others, it wouldn't be as nearly as damaging to their cause. It is because this dogmatic way of thinking is so engrained and prevalent within nutritional establishments, that it has been witnessed by far too many. Years and years of ridiculing others, their level of knowledge - everybody is sick and tired of it now.